Question on Limb Pad Angle for ILF Riser

[mmattockx]

This is mainly for Kirk because he has spent a lot of time tinkering with this, but all thoughts/experiences are welcome.

I am laying out a 25" wood ILF riser because I want to have easily swapped limbs for weight changes but I don't want to use an ugly aluminum riser. So far I just took some pictures from websites and then drew over top of them in autocad to get the rough dimensions. Most of them seem to be around 18-20 degree pad angles, with the pads set back a bit behind the deepest part of the grip. Because you can tune the limb angles a bit with ILF fittings the pad angle may not be so critical, but the adjustment range isn't huge and it affects the brace height and string tension at brace.

So, my question is what the trade offs are between setting the pads back/forward relative to the grip and using less/more pad angle? I understand this will only be generalities but I have never played with this and wanted to kind of get an idea of what the interactions tend to be or where things might trend.


Thanks,
Mark

[B-JS]

I would not recommend to Change the relative Position and Angle much.
ILF Limbs are designed to be mounted in a specific Angle.
If you Change that a Lot, you may Overstress the limbs or loose Performance.

[Kirkll]

Standard ILF limb pad angles are 17 degree.  The adjustment on those bolts are for fine tuning tiller and preload for different set ups and limb designs. They are Not for adjusting draw weight. Different limb designs are going to have different settings to maximize the performance.

I've always balanced the  ILF limbs i build at about one full turn off the bottom at even tiller.

Building 25" ILF risers from wood requires reinforcement of some kind. Even 40# limbs will flex those long risers a lot. I build 21'' risers and use a G-10 I beam assembly, and that length will handle up to 65-70# limbs with out  much flex at all. Using a good high density hardwood I-beam works well too for lighter draw weight target limbs. Its rare to see a long riser target bow much over 45# in draw weight.

Food for thought.      Kirk

[mmattockx]

Standard ILF limb pad angles are 17 degree.

Thanks for the thoughts, Kirk. Is there somewhere I can go to find the ILF standard or is that something that doesn't seem to exist in public?


Mark

[Kirkll]

When i first started building ILF rigs about 10 years ago i got all my specs from Lancaster archery supply. They sold a lot of those Trad Tech risers in the day...I got all the industry standards from them, and then started building my own. They cater to a lot of Target archers.    Kirk

[Kirkll]

The challenging thing about building ILF risers is Getting them cut past center far enough so the archer can use different types of rests and plungers. 3/8" to 1/2" past center is tricky to build.

Target archers shooting indoor leagues in general seem to shoot closer to center shot set ups so arrow spine can be mitigated and use larger diameter shafts.  "Line cutters" . I used to shoot 2512 aluminum shafts when i was shooting Vegas rounds, and NFAA rounds with a center shot set up and a back tension rope release aid.....

You were not even in the running unless you were shooting perfect 300 rounds consistently, and just counting X's. You had to be in the 20X range to take home the money at tournaments.   Kirk

[mmattockx]

The challenging thing about building ILF risers is Getting them cut past center far enough so the archer can use different types of rests and plungers. 3/8" to 1/2" past center is tricky to build.

Since this is just for me I am not going to cut it much past center and I will be doing a structural analysis of the final design to be comfortable with the margin it has. Making a wood riser cut that far past center would sure be a challenge and need some composite materials mixed in.


Mark

[Kirkll]

I've got one in the spray booth right now that is a 17" version. Here it is with a sanding sealer before i finish sanded it. This one is only cut 1/8" past center for shooting off the shelf.

The ones i build i use a G-10 frame on the back as well as an I - Beam. It gives it excellent mass weight for even a shorter riser length. That G-10 is heavy stuff.

[OldRawhide42]

Kirk how thick is the G10 I beam. It looks like it is on center.

[Kirkll]

This one is a 1/4" thick , and pretty close to center on lay up. Maybe offset a 1/8" after milling the riser. This one isn't cut past center much at all.  maybe 3/32"  . I can go pretty thin on this I-beam with the full G-10 overlay on the back.  Typically i'll run a 3/8" G-10 , and off set them 1/4" for a plunger set up.   Kirk